[PATCH v3 iproute2] bridge: add support for L2 multicast groups

[Vladimir Oltean]

Extend the 'bridge mdb' command for the following syntax:
bridge mdb add dev br0 port swp0 grp 01:02:03:04:05:06 permanent

Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
---
Changes in v3:
- Using rt_addr_n2a_r instead of inet_ntop/ll_addr_n2a directly.
- Updated the bridge manpage.

Changes in v2:
- Removed the const void casts.
- Removed MDB_FLAGS_L2 from the UAPI to be in sync with the latest
  kernel patch:
  https://patchwork.ozlabs.org/project/netdev/patch/20201028233831.610076-1-vladimir.oltean@xxxxxxx/

 bridge/mdb.c                   | 54 ++++++++++++++++++++++++++--------
 include/uapi/linux/if_bridge.h |  1 +
 man/man8/bridge.8              |  8 ++---
 3 files changed, 46 insertions(+), 17 deletions(-)

diff --git a/bridge/mdb.c b/bridge/mdb.c
index 4cd7ca762b78..ef89258bc5c3 100644
--- a/bridge/mdb.c
+++ b/bridge/mdb.c
@@ -149,6 +149,7 @@ static void print_mdb_entry(FILE *f, int ifindex, const struct br_mdb_entry *e,
 			    struct nlmsghdr *n, struct rtattr **tb)
 {
 	const void *grp, *src;
+	const char *addr;
 	SPRINT_BUF(abuf);
 	const char *dev;
 	int af;
@@ -156,9 +157,16 @@ static void print_mdb_entry(FILE *f, int ifindex, const struct br_mdb_entry *e,
 	if (filter_vlan && e->vid != filter_vlan)
 		return;
 
-	af = e->addr.proto == htons(ETH_P_IP) ? AF_INET : AF_INET6;
-	grp = af == AF_INET ? (const void *)&e->addr.u.ip4 :
-			      (const void *)&e->addr.u.ip6;
+	if (!e->addr.proto) {
+		af = AF_PACKET;
+		grp = &e->addr.u.mac_addr;
+	} else if (e->addr.proto == htons(ETH_P_IP)) {
+		af = AF_INET;
+		grp = &e->addr.u.ip4;
+	} else {
+		af = AF_INET6;
+		grp = &e->addr.u.ip6;
+	}
 	dev = ll_index_to_name(ifindex);
 
 	open_json_object(NULL);
@@ -168,9 +176,14 @@ static void print_mdb_entry(FILE *f, int ifindex, const struct br_mdb_entry *e,
 	print_string(PRINT_ANY, "port", " port %s",
 		     ll_index_to_name(e->ifindex));
 
+	/* The ETH_ALEN argument is ignored for all cases but AF_PACKET */
+	addr = rt_addr_n2a_r(af, ETH_ALEN, grp, abuf, sizeof(abuf));
+	if (!addr)
+		return;
+
 	print_color_string(PRINT_ANY, ifa_family_color(af),
-			    "grp", " grp %s",
-			    inet_ntop(af, grp, abuf, sizeof(abuf)));
+			    "grp", " grp %s", addr);
+
 	if (tb && tb[MDBA_MDB_EATTR_SOURCE]) {
 		src = (const void *)RTA_DATA(tb[MDBA_MDB_EATTR_SOURCE]);
 		print_color_string(PRINT_ANY, ifa_family_color(af),
@@ -440,6 +453,25 @@ static int mdb_show(int argc, char **argv)
 	return 0;
 }
 
+static int mdb_parse_grp(const char *grp, struct br_mdb_entry *e)
+{
+	if (inet_pton(AF_INET, grp, &e->addr.u.ip4)) {
+		e->addr.proto = htons(ETH_P_IP);
+		return 0;
+	}
+	if (inet_pton(AF_INET6, grp, &e->addr.u.ip6)) {
+		e->addr.proto = htons(ETH_P_IPV6);
+		return 0;
+	}
+	if (ll_addr_a2n((char *)e->addr.u.mac_addr, sizeof(e->addr.u.mac_addr),
+			grp) == ETH_ALEN) {
+		e->addr.proto = 0;
+		return 0;
+	}
+
+	return -1;
+}
+
 static int mdb_modify(int cmd, int flags, int argc, char **argv)
 {
 	struct {
@@ -497,14 +529,10 @@ static int mdb_modify(int cmd, int flags, int argc, char **argv)
 	if (!entry.ifindex)
 		return nodev(p);
 
-	if (!inet_pton(AF_INET, grp, &entry.addr.u.ip4)) {
-		if (!inet_pton(AF_INET6, grp, &entry.addr.u.ip6)) {
-			fprintf(stderr, "Invalid address \"%s\"\n", grp);
-			return -1;
-		} else
-			entry.addr.proto = htons(ETH_P_IPV6);
-	} else
-		entry.addr.proto = htons(ETH_P_IP);
+	if (mdb_parse_grp(grp, &entry)) {
+		fprintf(stderr, "Invalid address \"%s\"\n", grp);
+		return -1;
+	}
 
 	entry.vid = vid;
 	addattr_l(&req.n, sizeof(req), MDBA_SET_ENTRY, &entry, sizeof(entry));
diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
index 69b99901fc5a..db41a5ff34af 100644
--- a/include/uapi/linux/if_bridge.h
+++ b/include/uapi/linux/if_bridge.h
@@ -526,6 +526,7 @@ struct br_mdb_entry {
 		union {
 			__be32	ip4;
 			struct in6_addr ip6;
+			unsigned char mac_addr[ETH_ALEN];
 		} u;
 		__be16		proto;
 	} addr;
diff --git a/man/man8/bridge.8 b/man/man8/bridge.8
index 84b9b70c7dea..b3414ae31faf 100644
--- a/man/man8/bridge.8
+++ b/man/man8/bridge.8
@@ -665,7 +665,7 @@ the bridge to which this address is associated.
 .SH bridge mdb - multicast group database management
 
 .B mdb
-objects contain known IP multicast group addresses on a link.
+objects contain known IP or L2 multicast group addresses on a link.
 
 .P
 The corresponding commands display mdb entries, add new entries,
@@ -685,11 +685,11 @@ the port whose link is known to have members of this multicast group.
 
 .TP
 .BI grp " GROUP"
-the IP multicast group address whose members reside on the link connected to
-the port.
+the multicast group address (IPv4, IPv6 or L2 multicast) whose members reside
+on the link connected to the port.
 
 .B permanent
-- the mdb entry is permanent
+- the mdb entry is permanent. Optional for IPv4 and IPv6, mandatory for L2.
 .sp
 
 .B temp
-- 
2.25.1